We propose to evaluate relationships among trajectories (initiation, progression, and speed of progression) for alcohol, tobacco, and marijuana use and how macro-social and parental factors and their interactions influence these trajectories. We also plan to investigate the trajectory of inhalant use and its relationship to other substances. Macro-social influences of interest include policy and programmatic interventions aimed at curbing tobacco use (e.g., cigarette excise taxes, antismoking campaigns, state tobacco control program investments), alcohol use (e.g., state alcohol taxes and control laws, stringency of law enforcement), and marijuana use (e.g., penalties for possession, enforcement of drug laws, drug prices). While some studies have examined the influence of these macro-social influences on alcohol and tobacco, and marijuana separately, few have examined how policies and programs aimed at tobacco and alcohol may not only curb the use of the targeted drug but may also have spillover effects for marijuana. Such analyses have important policy implications and can provide unique insights into how curbing potential "gateway" substances may affect initiation and progression of marijuana use. Parent-child communication about drugs has been suggested as a protective factor, but little direct evidence is available on this aspect of parenting. Much of the research measures the presence or absence of parent-child communication about drugs but does not address the content of such communication. Moreover, parent-child communication may vary in nature throughout adolescence, suggesting that the temporal nature of the discourse might be an important factor in understanding drug risk socialization. The age at which different types of communication occur (e.g., about rules, consequences and circumstances, media influences) may be important to understanding how parents socialize adolescents regarding drugs. We will assess the extent to which the influence of parent-child communications about drug use is moderated by (or interacts with) other parental characteristics (e.g., parental monitoring) and other levels of contextual influence, including macro-level policy changes and interventions. Specific aims are as follows: (1) Investigate how the initiation, progression, and intensity of alcohol and tobacco use influence the initiation, progression, and intensity of marijuana use. Determine how inhalant use relates to the use, progression, and severity of use of other substances. (2) Test the influence of alcohol, tobacco, and marijuana policies and intervention on the use of the targeted substance and related substances. (3) Investigate how the frequency and content of parent-child communication about drug use affects the development of adolescent drug use. (4) Explore how potential interactions between macro-social policies and interventions and parental communication influences the development of adolescent drug use. Generalized Growth Mixture Modeling will be used to test the study hypotheses.